Screen and projector

ABSTRACT

A screen includes a plurality of structures arrayed in parallel in at least one direction of a first direction and a second direction perpendicular to the first direction on a reference surface parallel to the first direction and the second direction. The structures are arrayed such that at least one of a distance between central positions of the structures adjacent to each other and a size of the structure changes irregularly in at least one direction, in which the structures are arrayed in parallel, of the first and second directions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of JP 2008-067207 filed in Japan onMar. 17, 2008, the entire disclosure of which is hereby incorporated byreference in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to a screen and a projector and inparticular, to a technique of a screen that reflects light correspondingto an image signal.

2. Related Art

A so-called reflective screen that reflects light corresponding to animage signal is requested to have a high reflectance in order to obtaina bright image. In addition, the reflective screen is requested to havea good viewing angle characteristic allowing light distributed atsuitable angles to propagate in a direction toward a viewer. A knowntechnique for obtaining a high reflectance and a good viewing anglecharacteristic in a screen is proposed in JP-A-2006-215162, for example.In the technique proposed in JP-A-2006-215162, the high reflectance andthe good viewing angle characteristic are obtained by providing areflective portion in a portion of a plurality of fine structuresarrayed regularly on which light corresponding to an image signal isincident.

When displaying an image using light corresponding to an image signal, amoire may be generated due to diffraction of light caused by periodicpatterns. The moire causes deterioration of the image quality by makinga color or a pattern, which is not present in an original image signal,appear. The moire is noticeably generated when structures formed on ascreen are fine and the structures are regularly arrayed. In addition,the moire becomes conspicuous as the reflectance of the screenincreases. Thus, according to the known technique, a problem in that itis difficult to obtain a bright and high-quality image occurs.

SUMMARY

An advantage of some aspects of the invention is that it provides ascreen and a projector capable of obtaining a bright image by a highreflectance and a good viewing angle characteristic and displaying ahigh-quality image by reducing generation of a moire.

According to an aspect of the invention, there is provided a screenincluding a plurality of structures arrayed in parallel in at least onedirection of a first direction and a second direction perpendicular tothe first direction on a reference surface parallel to the firstdirection and the second direction. The structures are arrayed such thatat least one of a distance between central positions of the structuresadjacent to each other and a size of the structure changes irregularlyin at least one direction, in which the structures are arrayed inparallel, of the first and second directions.

The size of the structure is assumed to refer to a magnification ratioof the shape of each structure to the shape as a reference. Diffractionof light caused by periodicity is reduced by irregularly changing atleast one of the distance between the central positions of thestructures and the size of the structure. By using the plurality ofstructures arrayed to have irregularity, it becomes possible to reducegeneration of a moire while realizing a high reflectance. Accordingly,it is possible to obtain a screen in which a bright image can beobtained by the high reflectance and the good viewing anglecharacteristic and a high-quality image can be displayed by reducing thegeneration of a moire. In the screen according to the aspect of theinvention, the generation of a moire caused by superposition of aplurality of periodic patterns can be reduced, and generation of aninterference fringe caused by diffraction at the structures provided inthe screen can also be reduced.

Furthermore, in the screen according to the aspect of the invention, itis preferable that the structures be arrayed such that at least one ofthe distance between the central positions and the size changesirregularly in the first and second directions. By arraying theplurality of structures having irregularity in the first and seconddirections, the generation of a moire can be reduced more effectively.

Furthermore, in the screen according to the aspect of the invention, itis preferable that the structures be arrayed such that an upper limit ofa distance between a predetermined reference position and the centralposition is 5% or more and less than 50% of a predetermined referencelength in at least one direction of the first and second directions. Thereference position is assumed to refer to the central position of thestructure when arraying each structure with the distance as a referencelength. By changing the distance between the central positions of thestructures in such a range, the generation of a moire can be reducedeffectively and a high reflectance and a good viewing anglecharacteristic can be obtained.

Furthermore, in the screen according to the aspect of the invention, itis preferable that upper and lower limits of a width of the structure inat least one direction of the first and second directions be lengthschanged from a reference width by a length equivalent to 5% or more andless than 50% of the predetermined reference width. By changing the sizeof the structure in such a range, the generation of a moire can bereduced effectively and a high reflectance and a good viewing anglecharacteristic can be obtained.

Furthermore, in the screen according to the aspect of the invention, itis preferable to further include a reflective portion that is formed ona surface of the structure and reflects light. In this case, a highreflectance can be realized.

Furthermore, in the screen according to the aspect of the invention, itis preferable to further include an absorption portion that is formed ona surface of the structure and absorbs light. In this case, it ispossible to reduce reflection of outside light which is not necessaryfor display of an image and to display an image with high contrast.

Furthermore, in the screen according to the aspect of the invention, itis preferable that the structure have approximately the same shape as apart of a spherical body. In this case, a good viewing anglecharacteristic can be realized by the structures that can be relativelyeasily formed.

In addition, according to another aspect of the invention, there isprovided a projector that includes the screen described above anddisplays an image by projecting light onto the screen. A bright andhigh-quality image can be displayed by providing the screen. As aresult, a projector capable of displaying a bright and high-qualityimage can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a view schematically illustrating the cross-sectionalconfiguration of main parts of a screen according to a first embodimentof the invention;

FIG. 2 is a view illustrating the arrangement of structures in acomparative example of the first embodiment;

FIG. 3 is a view illustrating the arrangement of structures in the firstembodiment;

FIG. 4 is a view illustrating the change of the central position to thereference position;

FIG. 5 is a view illustrating an example of a case in which structuresare arrayed without gaps therebetween;

FIG. 6 is a view illustrating the arrangement of structures in a firstmodification of the first embodiment;

FIG. 7 is a view illustrating the arrangement of structures in a secondmodification of the first embodiment;

FIG. 8 is a view illustrating the arrangement of structures in a secondembodiment of the embodiment;

FIG. 9 is a view illustrating the arrangement of structures in amodification of the second embodiment;

FIG. 10 is a view schematically illustrating the configuration of aprojector according to a third embodiment of the invention; and

FIG. 11 is a view schematically illustrating the configuration of aprojection engine portion.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the invention will be described in detailwith reference to the accompanying drawings.

First Embodiment

FIG. 1 is a view schematically illustrating the cross-sectionalconfiguration of main parts of a screen 10 according to a firstembodiment of the invention. A substrate 11 is a parallel flat platehaving a reference surface S1 which is a flat surface. The referencesurface S1 is a surface parallel to an X-axis direction, which is afirst direction, and a Y-axis direction, which is a second directionperpendicular to the first direction. The X-axis direction is ahorizontal direction, for example. The Y-axis direction is a verticaldirection, for example. The X axis is an axis parallel to the referencesurface S1. The Y axis is an axis which is perpendicular to the X axisand is parallel to the reference surface S1 on the substrate 11. A Zaxis is an axis perpendicular to the X axis and the Y axis. The crosssection shown in the drawing is a YZ cross section perpendicular to thereference surface S1.

A plurality of structures 12 are disposed on the reference surface S1.The structure 12 has a protruding shape which is approximately the sameas a part of a spherical body obtained by cutting the spherical bodyalong the flat surface. In the cross section shown in the drawing, thestructure 12 has an approximately semicircular shape. The structure 12is formed by using a resin member, for example, an ultraviolet curableresin or foamed ink. The plurality of structures 12 are arrayed inparallel in the two-dimensional direction of the X-axis and Y-axisdirections. The plurality of structures 12 are arrayed at distancestherebetween.

A reflective portion 13 reflects light. The reflective portion 13 isprovided in a portion, on which projection light L1 from an emissionposition set beforehand for the screen 10 is incident, of a surface ofthe structure 12. In the structure 12 shown in the drawing, thereflective portion 13 is provided at the vertical lower half of thesurface of the structure 12. The reflective portion 13 is formed byapplying a highly reflective white coating material or silver coatingmaterial on the surface of the structure 12, for example. By forming thereflective portion 13 on the curved surface of the structure 12, theprojection light L1 reflected from the reflective portion 13 is diffusedtoward a viewer side. The high reflectance of the screen 10 can berealized by providing the reflective portion 13. In addition, the goodviewing angle characteristic of the screen 10 can be realized bydiffusing the projection light L1 toward the viewer side. In addition,the structure 12 may also be formed by using a highly reflective member,for example, a milky (translucent) material. In this case, a portion ofthe surface of the structure 12 other than a portion where an absorptionportion 14 is provided functions as a reflective portion.

The absorption portion 14 absorbs light. The absorption portion 14 isprovided in a portion other than the portion, on which the projectionlight L1 from the emission position set beforehand for the screen 10 isincident, of the surface of the structure 12. In the structure 12 shownin the drawing, the absorption portion 14 is provided at the verticalupper half of the surface of the structure 12. The absorption portion 14is formed by applying a light-absorbing resin member on the surface ofthe structure 12, for example. The absorption portion 14 absorbs lightincident from a different direction from the projection light L1, forexample, outside light L2 which is not necessary for display of animage. The screen 10 can display a high-contrast image thereon byreducing reflection of the outside light L2 using the absorption portion14. In addition, the structure 12 may also be formed by using alight-absorbing member, for example, a black material. In this case, aportion of the surface of the structure 12 other than a portion wherethe reflective portion 13 is provided functions as an absorptionportion.

FIG. 2 is a view explaining the arrangement of the structures 12 in acomparative example of the present embodiment. The comparative exampleis the same as the present embodiment except that the arrangement of thestructures 12 is different from that in the present embodiment. On theXY plane shown in the drawing, each structure 12 has a circular shapewith an approximately fixed diameter D. The structures 12 are arrayedcontinuously in both the X-axis direction and the Y-axis direction. Thestructures 12 are arrayed to deviate by 1/2 pitch between adjacentcolumns in both the X-axis direction and the Y-axis direction.

A central position O′ is the center of a surface of the structure 12facing the reference surface S1. A distance d1 between the centralpositions O′ of the structures 12 adjacent to each other in the Xdirection is approximately constant. In addition, a distance d2 betweenthe central positions O′ of the structures 12 adjacent to each other inthe Y direction is approximately constant. As the distances d1 and d2and the diameter D decrease, the fineness of the screen 10 increases butit becomes difficult to manufacture the screen 10. In addition, as thedistances d1 and d2 and the diameter D increase, it becomes easy tomanufacture the screen 10 but the resolution is reduced. Inconsideration of difficulties in manufacture or an effect on theresolution, the distance d1 in the X-axis direction and the distance d2in the Y-axis direction are set to about several tens of micrometers to1 mm, for example. The diameter D of the structure 12 is set to aboutseveral tens of micrometers to 1 mm, for example.

When straight lines L1 arrayed in parallel at distances of d1/2 in theX-axis direction and straight lines L2 arrayed in parallel at distancesof d2/2 in the Y-axis direction are assumed, the central position O′ ison a point of intersection between the straight line L1 and the straightline L2. Thus, in this comparative example, the structures 12 arearrayed in a regular manner. When the structure 12 is fine and thearrangement of the structures 12 is regular, generation of a moirebecomes noticeable. In addition, the moire becomes conspicuous as thereflectance of the screen increases.

FIG. 3 is a view explaining the arrangement of the structures 12 in thepresent embodiment. Compared with the case of the comparative example,the present embodiment is characterized in that a distance betweencentral positions O of the structures 12 adjacent to each other is madeto change irregularly. Hereinafter, an explanation will be made assumingthat the central position O′ of the structure 12 in the case of thecomparative example shown in FIG. 2 is a reference position, thedistance d1 between the central positions O in the X-axis direction is areference length in the X-axis direction, and the distance d2 betweenthe central positions O′ in the Y-axis direction is a reference lengthin the Y-axis direction.

FIG. 4 is a view explaining the change of the central position O to thereference position O′. In both the X-axis direction and the Y-axisdirection, it is assumed that directions of arrows indicating axes areplus and directions opposite the arrows are minus. The central positionO moves from the reference position O′ by a length Δx in the plus X-axisdirection or minus X-axis direction and a length Δy in the plus Y-axisdirection or minus Y-axis direction. Δx is a distance between thereference position O′ and the central position O in the X-axisdirection. Δy is a distance between the reference position O′ and thecentral position O in the Y-axis direction. The central position O shownin the drawing moves in the plus X-axis direction and the plus Y-axisdirection from the reference position O′.

Lower limits of Δx and Δy are all zero. When Δx is zero, the centralposition O is on the same straight line L1 as the reference position O′.When Δy is zero, the central position O is on the same straight line L2as the reference position O′. When Δx and Δy are all zero, the centralposition O matches the reference position O′. An upper limit Δxmax of Δxis a length equivalent to 5% or more and less than 50% of the referencelength d1 in the X-axis direction. For example, the upper limit Δxmax ofΔx is a length equivalent to 10% of the reference length d1. An upperlimit Δymax of Δy is a length equivalent to 5% or more and less than 50%of the reference length d2 in the Y-axis direction. For example, theupper limit Δymax of Δy is a length equivalent to 10% of the referencelength d2. The central position O is a certain position in a rectangularregion AR the length of which in the X-axis direction is 2Δxmax, thelength of which in the Y-axis direction is 2Δymax, and the center ofwhich is the reference position O′.

By randomly changing Δx and Δy in each structure 12, the centralposition O may be changed randomly. By randomly setting the centralposition O of each structure 12, each structure 12 is provided in acondition where the distance between the central positions O of thestructures 12 adjacent to each other is irregularly changed in theX-axis and Y-axis directions. Diffraction of light caused by periodicityis reduced by irregularly changing the distance between the centralpositions O.

It can be seen that an effect of reducing the generation of a moire isobtained by randomly changing the central position O in a conditionwhere Δxmax and Δymax are within a range of 5% or more of the referencelengths d1 and d2. When Δxmax and Δymax are set to lengths equivalent to50% or more of the reference lengths d1 and d2, the structures 12adjacent to each other may overlap. When the periodicity is so adverselyaffected that the structures 12 adjacent to each other overlap, thereflectance or the viewing angle characteristic considered may not beobtained. In order to obtain a high reflectance and a good viewing anglecharacteristic, it is desirable that Δxmax and Δymax be less than 50% ofthe reference lengths d1 and d2.

Therefore, by setting Δxmax and Δymax to the lengths equivalent to 5% ormore and less than 50% of the reference lengths d1 and d2, it ispossible to obtain a bright image and to reduce the generation of amoire. Preferably, by setting Δxmax and Δymax to the lengths equivalentto about 10% to 15% of the reference lengths d1 and d2, it is possibleto obtain a brighter image and to effectively reduce the generation of amoire. As described above, effects that a bright image can be obtainedby the high reflectance and the good viewing angle characteristic and ahigh-quality image can be displayed by reducing the generation of amoire are obtained. According to the embodiment of the invention, themoire generated by overlapping of a plurality of periodic patterns (inthe present embodiment, a pattern of a pixel caused by the projectionlight L1 and a pattern of a periodic structure that the screen 10 has)can be reduced. In addition, the screen 10 according to the embodimentof the invention can also reduce the generation of an interferencefringe generated by diffraction at the structures 12 provided in thescreen 10 regardless of the periodicity of the projection light L1.

The viewing angle characteristic of the screen 10 is determined bysuitably setting the reference length d1 in the X-axis direction and thereference length d2 in the Y-axis direction. For example, by settingd1<d2, it becomes possible to view a bright image in a wide range in thehorizontal direction compared with the vertical direction. In addition,the reference lengths d1 and d2 do not necessarily need to be fixedlengths on the entire screen 10. The reference lengths d1 and d2 mayalso be set to change according to the distance from the emissionposition set beforehand for the screen 10. In this case, the referencelengths d1 and d2 are approximately fixed lengths partially but aredifferent lengths in portions spaced apart from each other on the screen10.

The structure 12 is formed, for example, by transferring a shape formedin a mold to a material member. The mold used for the transfer is formedby using a photolithographic technique, for example. A mold with adesired shape is formed by performing etching processing afterpatterning the resist applied on the substrate. The structure 12 withapproximately the same shape as a part of a spherical body can berelatively easily formed by using such a method. In addition, bysuitably controlling the resist removal position when forming the mold,the positions of the structures 12 can be easily adjusted such that thedistance between the central positions O changes irregularly. Inaddition, the structures 12 may also be formed by using any kind ofmethod used in the related art.

The structures 12 do not necessarily need to be arrayed at distancestherebetween. For example, as shown in FIG. 5, the structures 12 may bearrayed without gaps therebetween. By arraying the structures 12 withoutgaps therebetween, each of the structures 12 has a hexagonal shape onthe XY plane. For example, when the structures 12 with the diameter D of200 μm are arrayed without gaps therebetween, the reference length d1 inthe X-axis direction and the reference length d2 in the Y-axis directionare set to 100 μm and 200 μm, respectively. Also in this case, theeffect of reducing the generation of a moire can be obtained byirregularly changing the distance between the central positions of thestructures 12.

The structures 12 may be arrayed to deviate by a pitch other than 1/2pitch between adjacent columns in the X-axis and Y-axis directions ormay be arrayed in a matrix such that the structures 12 do not deviatebetween the adjacent columns. The structure 12 does not necessarily needto have approximately the same shape as a part of the spherical body.The structure 12 may also have a shape with an aspheric surface, anadjustable surface, or a flat surface instead of a spherical surface.For example, the structure 12 may have approximately the same shape as apart of an ellipsoidal surface, a conical shape, or a pyramid shape. Inaddition, the structure 12 does not necessarily need to have aprotruding shape and may have a recessed shape.

FIG. 6 is a view explaining the arrangement of the structures 12 in afirst modification of the present embodiment. This modification ischaracterized in that the distance between the central positions O ismade to change irregularly only in the Y-axis direction of the X-axisand Y-axis directions. The central positions O are all on the straightline L1. The structures 12 are arrayed such that the distance betweenthe central positions O of the structures 12 adjacent to each other inthe X-axis direction is the reference length d1 (Δx=0). For the Y-axisdirection, the central position O of each structure 12 is randomly setin the same manner as described using FIG. 4. An upper limit Δymax of Δyis a length equivalent to 5% or more and less than 50% of the referencelength d2 in the Y-axis direction. For example, the upper limit Δymax ofΔy is assumed to be a length equivalent to 10% of the reference lengthd2.

Thus, the effect of reducing the generation of a moire can be obtainedby irregularly changing the distance between the central positions O atleast in one direction. In addition, the distance between the centralpositions O of the structures 12 may also be made to change irregularlyonly in the X-axis direction of the X-axis and Y-axis directions. Inthis case, the structures 12 are arrayed such that the distance betweenthe central positions O of the structures 12 adjacent to each other inthe Y-axis direction is the reference length d2 (Δy=0). An upper limitΔxmax of Δx is a length equivalent to 5% or more and less than 50% ofthe reference length d1 in the X-axis direction. For example, the upperlimit Δxmax of Δx is a length equivalent to 10% of the reference lengthd1.

FIG. 7 is a view explaining the arrangement of structures 20 in a secondmodification of the present embodiment. In this modification, thestructures 20 are arrayed in parallel only in the X-axis direction ofthe X-axis and Y-axis directions. Each structure 20 has a shape which islonger in the Y-axis direction than the X-axis direction. Each structure20 has a protruding shape which is approximately the same as a shapeobtained by cutting a cylinder along a plane perpendicular to bottom andtop surfaces of the cylinder.

A centerline P is a straight line that equally divides a rectangularshape of the structure 20, which is in contact with the referencesurface S1, in the X-axis direction and is approximately parallel to theY axis. The centerline P is a central position of the structure 20 inthe X-axis direction. The structures 20 are arrayed such that a distancebetween the centerlines P adjacent to each other in the X-axis directionchanges irregularly. Also in this modification, an upper limit of thelength from the reference position to the centerline P is a lengthequivalent to 5% or more and less than 50% of the reference length inthe X-axis direction. For example, the upper limit of the length fromthe reference position to the centerline P is a length equivalent to 10%of the reference length. By irregularly changing the distance betweenthe centerlines P of the structures 20 in the X-axis direction in whichthe structures 20 are arrayed in parallel, the effect of reducing thegeneration of a moire can be obtained. Alternatively, in thismodification, structures which are longer in the X-axis direction thanthe Y-axis direction may be arrayed in parallel in the Y-axis direction.Also in this case, the effect of reducing the generation of a moire canbe obtained by irregularly changing the distance between the centerlinesP in the Y-axis direction in which the structures are arrayed inparallel.

Second Embodiment

FIG. 8 is a view explaining the arrangement of structures 30 in a secondembodiment of the invention. The structure 30 described in the presentembodiment is applied to the screen 10 according to the firstembodiment. The present embodiment is characterized in that thestructures 30 whose sizes change irregularly are arrayed in parallel inthe X-axis and Y-axis directions. The same components as in the firstembodiment are denoted by the same reference numerals, and a repeatedexplanation thereof will be omitted.

The structures 30 have shapes which are approximately the same as a partof a spherical body and have similar shapes. The size of each structure30 is changed by changing a magnification of a shape used as areference. A distance d1 between the central positions O′ of thestructures 30 adjacent to each other in the X direction is approximatelyconstant. In addition, a distance d2 between the central positions O′ ofthe structures 30 adjacent to each other in the Y direction isapproximately constant. The central position O′ is on a point ofintersection between the straight line L1 and the straight line L2.

Hereinafter, an explanation will be made by setting the diameter D ofthe structure 12 in the comparative example shown in FIG. 2 as areference width of the structure 30 in the X-axis and Y-axis directionsthereof in the present embodiment. A lower limit of the diameter of eachstructure 30 is a length larger than 50% of the reference width D andequal to or smaller than 95% of the reference width D. For example, thelower limit of the diameter of each structure 30 is a length equivalentto 90% of the reference width D. An upper limit of the diameter of eachstructure 30 is a length equivalent to 105% or more and less than 150%of the reference width D. For example, the upper limit of the diameterof each structure 30 is a length equivalent to 110% of the referencewidth D. Thus, the upper and lower limits of the diameter of eachstructure 30 are assumed to be lengths changed from the reference widthD by a length equivalent to 5% or more and less than 50% of thereference width D.

The width of each structure 30 in the X-axis direction and the width ofeach structure 30 in the Y-axis direction are changed by changing thediameter of each structure 30. By randomly setting the diameter of eachstructure 30, the structures 30 are provided such that the size of eachstructure 30 changes irregularly. Generation of a moire can be reducedby randomly changing the diameter in a condition where the lengthschanged by 5% or more from the reference width D are set as the upperand lower limits. When the lengths changed by 50% or more from thereference width D are set as the upper and lower limits, the reflectanceor the viewing angle characteristic considered may not be obtainedbecause the structures 30 adjacent to each other may overlap each other.In order to obtain a high reflectance and a good viewing anglecharacteristic, it is desirable to set, as the upper and lower limits,the lengths changed less than 50% from the reference value D. Thus, bysetting the upper and lower limits of the diameter of each structure 30to the lengths changed from the reference width D by a length equivalentto 5% or more and less than 50% of the reference width D, it is possibleto obtain a bright image and to reduce the generation of a moire. Asdescribed above, also in the present embodiment, a bright image can beobtained by the high reflectance and the good viewing anglecharacteristic, and a high-quality image can be displayed by reducinggeneration of a moire and generation of an interference fringe.

Similar to the case of the first embodiment described above, thestructure 30 in the present embodiment is also formed by formation of amold using the photolithographic technique and transfer of the shapeformed in the mold to a material member. By suitably controlling theresist removal range when forming the mold, the shape of the structure30 can be easily adjusted such that the size of the structures 30changes irregularly. In addition, the structures 30 may also be formedby using any kind of method used in the related art.

The present embodiment is not limited to the case in which thestructures 30 whose sizes change irregularly are arrayed in parallel inboth the X-axis direction and the Y-axis direction. If the screen 10 hasa configuration in which the structures 30 whose sizes changeirregularly are arrayed in parallel in at least one direction of theX-axis and Y-axis directions, the effect of reducing the generation of amoire can be obtained. For example, the structures 30 with approximatelythe same size may be arrayed in parallel in one direction of the X-axisand Y-axis directions.

FIG. 9 is a view explaining the arrangement of the structures 30 in amodification of the present embodiment. This modification ischaracterized in that the structures 30 whose sizes change irregularlyare arrayed in parallel in the X-axis and Y-axis directions and thedistance between the central positions O changes irregularly in theX-axis and Y-axis directions. The arrangement of the central positions Oof the structures 30 are similar to the case of the first embodimentdescribed using FIGS. 3 and 4. By providing the structures 30 such thatthe size of the structure 30 and the distance between the centralpositions O of the structures 30 change irregularly, diffraction oflight caused by the periodicity can be further reduced compared with acase where either the size or the distance changes irregularly. As aresult, the generation of a moire can be reduced more effectively.

In the present embodiment, only one of the width of the structure 30 inthe X-axis direction and the width of the structure 30 in the Y-axisdirection may be changed in addition to the case in which both the widthin the X-axis direction and the width in the Y-axis direction arechanged. If the screen 10 has a configuration in which the size of thestructure 30 is irregularly changed by changing only one of the width inthe X-axis direction and the width in the Y-axis direction, the effectof reducing the generation of a moire can be obtained. For example, inthe case of a configuration having the structures 20 (refer to FIG. 7)which are long in the Y-axis direction, the width of the structure 20may be changed in the X-axis direction in which the structures 20 arearrayed in parallel.

Third Embodiment

FIG. 10 is a view schematically illustrating the configuration of aprojector 40 according to a third embodiment of the invention. Theprojector 40 has a projection engine portion 41 and the screen 10according to the above-described embodiment. A support portion 42supports the projection engine portion 41 and the screen 10. Theprojection engine portion 41 performs close projection from the positionof 1 m or less from a surface of the support portion 42 on which thescreen 10 is disposed, for example, from the position of about 30 cm.Light incident on the screen 10 from the projection engine portion 41 islargely inclined with respect to the normal of the reference surface S1(refer to FIG. 1). In addition, the projector 40 may have aconfiguration in which the projection engine portion 41 directlysupports the screen 10, for example, without being limited to the casein which the support portion 42 is provided.

FIG. 11 is a view schematically illustrating the configuration of theprojection engine portion 41. An ultra high pressure mercury lamp 51 isa light source unit that emits light components including red (R) light,green (G) light, and blue (B) light. A first integrator lens 52 and asecond integrator lens 53 each have a plurality of lens elements arrayedin the shape of an array. The first integrator lens 52 divides lightfrom the ultra high pressure mercury lamp 51 into a plurality of lightbeams. Each lens element of the first integrator lens 52 makes the lightbeams from the ultra high pressure mercury lamp 51 condensed near thelens element of the second integrator lens 53. The lens element of thesecond integrator lens 53 forms an image of the lens element of thefirst integrator lens 52 on a spatial light modulation device.

The light beams transmitted through the two integrator lenses 52 and 53are converted into linearly polarized light beams in the specificoscillating direction by a polarization conversion element 54. Asuperposition lens 55 makes an image of each lens element of the firstintegrator lens 52 superimposed on the spatial light modulation device.The first integrator lens 52, the second integrator lens 53, and thesuperposition lens 55 make the intensity distribution of light from theultra high pressure mercury lamp 51 uniform on the spatial lightmodulation device. The light from the superposition lens 55 is incidenton a first dichroic mirror 56. The first dichroic mirror 56 makes Rlight reflected therefrom and G light and B light transmittedtherethrough. The R light reflected by the first dichroic mirror 56 isincident on a field lens 58R for R light after an optical path of the Rlight is bent at the first dichroic mirror 56 and a reflecting mirror57. The field lens 58R for R light makes R light beams from thereflecting mirror 57 parallelized and the parallelized R beams incidenton a spatial light modulation device 59R for R light.

The spatial light modulation device 59R for R light is a spatial lightmodulation device that modulates R light according to an image signal,and is a transmissive liquid crystal display device. A liquid crystalpanel (not shown) provided in the spatial light modulation device 59Rfor R light has a liquid crystal layer interposed between twotransparent substrates in order to modulate light according to an imagesignal. The R light modulated by the spatial light modulation device 59Rfor R light is incident on a cross dichroic prism 60 that is a colormixing optical system.

The G light and the B light transmitted through the first dichroicmirror 56 are incident on a second dichroic mirror 61. The seconddichroic mirror 61 makes the G light reflected therefrom and the B lighttransmitted therethrough. The G light reflected by the second dichroicmirror 61 is incident on a field lens 58G for G light after an opticalpath of the G light is bent at the second dichroic mirror 61. The fieldlens 58G for G light makes the G light beams from the second dichroicmirror 61 parallelized and the parallelized G beams incident on aspatial light modulation device 59G for G light. The spatial lightmodulation device 59G for G light is a spatial light modulation devicethat modulates G light according to an image signal, and is atransmissive liquid crystal display device. The G light modulated by thespatial light modulation device 59G for G light is incident on a surfaceof the cross dichroic prism 60 different from the surface on which the Rlight is incident.

The B light transmitted through the second dichroic mirror 61 istransmitted through a relay lens 62, and then the optical path is bentby reflection at a reflecting mirror 63. The B light reflected from thereflecting mirror 63 is further transmitted through a relay lens 64.Then, the B light is incident on a field lens 58B for B light after theoptical path is bent by reflection at a reflecting mirror 65. Since theoptical path of B light is longer than the optical path of R light andthe optical path of G light, a relay optical system that uses the relaylenses 62 and 64 is adopted in the optical path of B light in order tomake an illumination rate in the spatial light modulation device for Blight equal to those for light components with the other colors.

The field lens 58B for B light makes B light beams from the reflectingmirror 65 parallelized and the parallelized B beams incident on aspatial light modulation device 59B for B light. The spatial lightmodulation device 59B for B light is a spatial light modulation devicethat modulates B light according to an image signal, and is atransmissive liquid crystal display device. The B light modulated by thespatial light modulation device 59B for B light is incident on a surfaceof the cross dichroic prism 60 different from the surface on which the Rlight is incident and the surface on which the G light is incident.

The cross dichroic prism 60 has two dichroic films 66 and 67 disposed tobe approximately perpendicular to each other. The first dichroic film 66makes the R light reflected therefrom and the G light and the B lighttransmitted therethrough. The second dichroic film 67 makes the B lightreflected therefrom and the R light and the G light transmittedtherethrough. The cross dichroic prism 60 mixes the R light, the Glight, and the B light incident from different directions and then emitsthe mixed light in the direction of a projection lens 68. The projectionlens 68 projects the light mixed by the cross dichroic prism 60 towardthe direction of the screen 10. An optical element for performing closeprojection with the light from the projection lens 68, for example, amirror with an aspheric shape may be used for the projection engineportion 41.

The projection engine portion 41 is not limited to having aconfiguration in which the ultra high pressure mercury lamp 51 is usedas a light source unit. It may also be possible to adopt a configurationin which a lamp other than the ultra high pressure mercury lamp 51, alight-emitting diode (LED), a laser light source, or the like is used asthe light source unit. The projection engine portion 41 is not limitedto having a configuration in which the spatial light modulation deviceis provided for every color light component, and may be configured tomodulate two or three or more color light components using one spatiallight modulation device.

By using the screen 10 according to the first embodiment, the projector40 can display a bright image with a high reflectance and a good viewingangle characteristic and can reduce the generation of a moire and thegeneration of an interference fringe. Accordingly, an effect that abright and high-quality image can be displayed is obtained. The screen10 according to the embodiment of the invention does not necessarilyneed to be used in a state of being united with the projection engineportion 41 in order to form the projector 40, and may also be used incombination with a projector disposed at the position distant from thescreen 10. The screen 10 does not necessarily need to be configured suchthat projection light largely inclined with respect to the normal of thereference surface S1 is incident on the screen 10. For example, thescreen 10 may be configured such that projection light slightly inclinedwith respect to the normal of the reference surface S1 is incident onthe screen 10. In addition, the configuration of the screen 10 accordingto the embodiment of the invention may also be applied to a transmissivescreen that allows light corresponding to an image signal to betransmitted therethrough. The projector 40 may also be a so-called rearprojector that supplies light onto one surface of a transmissive screenso that an image can be viewed by observing the light emitted from theother surface of the screen.

1. A screen comprising: a plurality of structures arrayed in parallel inat least one direction of a first direction, and in a second directionperpendicular to the first direction, on a reference surface parallel tothe first direction and the second direction, the structures beingarrayed such that at least one of a distance between central positionsof the structures adjacent to each other and a size of the structurechanges irregularly in at least one direction, in which the structuresare arrayed in parallel, of the first and second directions.
 2. Thescreen of claim 1, the structures being arrayed such that at least oneof the distance between the central positions and the size changesirregularly in the first and second directions.
 3. The screen of claim1, the structures being arrayed such that an upper limit of a distancebetween a predetermined reference position and the central position is5% to less than 50% of a predetermined reference length in at least onedirection of the first and second directions.
 4. The screen of claim 1,upper and lower limits of a width of each of the structures in at leastone direction of the first and second directions being changeable from apredetermined reference width by a length equivalent to 5% to less than50% of the predetermined reference width.
 5. The screen of claim 1,further comprising: a reflective portion that is formed on a surface ofthe structure and reflects light.
 6. The screen of claim 1, furthercomprising: an absorption portion that is formed on a surface of thestructure and absorbs light.
 7. The screen of claim 1, the structurehaving approximately the same shape as a part of a spherical body or acylindrical body.
 8. A projector comprising: the screen according toclaim 1, and a light source, an image being displayed by projectinglight onto the screen.
 9. A screen comprising: a substrate; an array ofconvex or concave portions disposed on the substrate, the convex orconcave portions having various sizes, or being disposed at variousdistances from each other.
 10. The screen of claim 9, each of the convexor concave portions having a reflective surface and an absorptionsurface.
 11. The screen of claim 9, the array of convex or concaveportions forming columns and rows, the convex or concave portions beingarrayed to deviate by a predetermined pitch between adjacent columns,and between adjacent rows.
 12. The screen of claim 9, each of theplurality of convex or concave portions having a center, a distancebetween each of the convex or concave portions in a first directionbeing approximately constant.
 13. The screen of claim 12, a distancebetween each of the convex or concave portions in a second directionbeing approximately constant.
 14. The screen of claim 12, a distancebetween each of the convex or concave portions in a second directionbeing irregular.
 15. The screen of claim 9, each of the plurality ofconvex or concave portions having a center, a distance between each ofthe convex or concave portions in a first direction being irregular. 16.The screen of claim 15, a distance between each of the convex or concaveportions in a second direction being irregular.
 17. The screen of claim16, the distance between adjacent convex or concave portions in thefirst direction and in the second distance being set at a firstpredetermined distance and at a second predetermined distance, theadjacent convex or concave portions in the first direction beingrandomly changeable from 5% to less than 50% of the predetermineddistance in the first direction, and the distance between adjacentconvex or concave portions in the second direction being randomlychangeable from 5% to less than 50% of the predetermined distance in thesecond direction.
 18. The screen of claim 15, the distance betweenadjacent convex or concave portions in a first direction being set at afirst predetermined distance and being randomly changeable from 5% toless than 50% of the first predetermined distance.
 19. The screen ofclaim 9, each of the plurality of convex or concave portions having apredetermined diameter randomly changeable from 5% to less than 50% ofthe predetermined diameter.
 20. A projector comprising: the screen ofclaim 9, and a light source, an image being displayed by projectinglight onto the screen.